253 research outputs found
The role of stellar radial motions in shaping galaxy surface brightness profiles
Aims. The physics driving features such as breaks observed in galaxy surface brightness (SB) profiles remains contentious. Here, we assess the importance of stellar radial motions in shaping their characteristics. Methods. We use the simulated Milky Way-mass cosmological discs from the Ramses Disc Environment Study (RaDES) to characterise the radial redistribution of stars in galaxies displaying type-I (pure exponentials), II (downbending), and III (upbending) SB profiles. We compare radial profiles of the mass fractions and the velocity dispersions of different sub-populations of stars according to their birth and current location. Results. Radial redistribution of stars is important in all galaxies regardless of their light profiles. Type-II breaks seem to be a consequence of the combined effects of outward-moving and accreted stars. The former produce shallower inner profiles (lack of stars in the inner disc) and accumulate material around the break radius and beyond, strengthening the break; the latter can weaken or even convert the break into a pure exponential. Further accretion from satellites can concentrate material in the outermost parts, leading to type-III breaks that can coexist with type-II breaks, but situated further out. Type-III galaxies would be the result of an important radial redistribution of material throughout the entire disc, as well as a concentration of accreted material in the outskirts. In addition, type-III galaxies display the most efficient radial redistribution and the largest number of accreted stars, followed by type-I and II systems, suggesting that type-I galaxies may be an intermediate case between types-II and III. In general, the velocity dispersion profiles of all galaxies tend to flatten or even increase around the locations where the breaks are found. The age and metallicity profiles are also affected, exhibiting different inner gradients depending on their SB profile, being steeper in the case of type-II systems (as found observationally). The steep type-II profiles might be inherent to their formation rather than acquired via radial redistribution
Síntesis y eficacia de formulaciones de liberación lenta del herbicida Mesotriona
Ponencia presentada en el XV Congreso de la Sociedad Española de Malherbología SEMh 2015 “La Malherbología y la Transferencia Tecnológica” Sevilla, 19 al 22 de octubre de 2015[ES]: Se ha comprobado la eficacia de formulaciones desarrolladas mediante complejos surfactante-sepiolita en la reducción de la lixiviación del herbicida mesotriona. Entre las formulaciones desarrolladas se ha escogido aquella que presentaba un perfil de liberación más lento en ensayos in vitro. Al aplicarse en columnas de suelo se observó una lixiviación del herbicida y acumulación con la formulación comercial en los segmentos inferiores a diferencia de la formulación desarrollada, que se correlacionaba con un incremento de la bioeficacia en los segmentos superiores. En experimentos en parcelas de campo, a diferencia de la formulación comercial, no se observó un rebrote de las malas hierbas al usar la formulación desarrollada.
[EN]: Synthesis and efficiency of slow release formulations of the herbicide mesotrione. The bioefficay of developed formulations based on surfactant-sepiolite complexes for reduced leaching of the herbicide mesotrione was tested. The formulation with a slower release pattern in in-vitro experiments was chosen for soil column and field experiments. In soil columns, the commercial formulation was leached and accumulated in the lower segments unlike the synthesized formulation, with a higher amount retained in the upper segments which was also correlated with a higher bioefficacy. In field experiments, a regrowth of weeds with the clay-based formulation was not observed, unlike the commercial formulation.Esta investigación ha recibido financiación a través de los proyectos CMT2009-07425 (MEC) cofinanciado por el Fondo Europeo de Desarrollo Regional (FEDER) y el Proyecto Bilateral Hispano-Argentino PRI-PIBAR-2011-1393 (MINECO-MINCYT). Carmen Galán agradece la beca Predoctoral disfrutada y asociada al Proyecto de Excelencia P09- RNM-4581.Peer Reviewe
Estimation of the Cooling Rate of Six Olive Cultivars Using Thermal Imaging
Bringing the olive harvest period forward leads to storing fruit in field temperatures that risk jeopardizing its quality. Knowledge about the bio-thermal characteristics of olives is crucial when considering their cooling, although published research on the subject is limited. In this work, the cooling rate of the fruit of six olive cultivars has been empirically determined by measuring the evolution of their low temperature under controlled conditions by thermal imaging. Based on these data, the cooling time needed to cool the fruit to 22 °C was estimated, considering the biometric characteristics of the individual fruit, a field temperature from 26 to 42 °C, and a room cooling temperature from −8 to −20 °C. The results showed differences among the cultivars and the need to further investigate the specific heat requirements for small varieties and the impact of the conduction factor on the heavier ones. The simulation suggests that between 2 min (for the light Arbequina and Koroneiki cultivars) and 5 min (for the heavier Verdial and Gordal cultivars) suffice to cool the fruit to the desired temperature with a room temperature of −16 °C. These results show the feasibility of developing technological solutions for cooling olives before their industrial processing with industrial applications such as cooling tunnels on individual fruit
Recovering star formation histories: Integrated-light analyses vs stellar colour-magnitude diagrams
Accurate star formation histories (SFHs) of galaxies are fundamental for
understanding the build-up of their stellar content. However, the most accurate
SFHs - those obtained from colour-magnitude diagrams (CMDs) of resolved stars
reaching the oldest main sequence turnoffs (oMSTO) - are presently limited to a
few systems in the Local Group. It is therefore crucial to determine the
reliability and range of applicability of SFHs derived from integrated light
spectroscopy, as this affects our understanding of unresolved galaxies from low
to high redshift.
To evaluate the reliability of current full spectral fitting techniques in
deriving SFHs from integrated light spectroscopy by comparing SFHs from
integrated spectra to those obtained from deep CMDs of resolved stars.
We have obtained a high signal--to--noise (S/N 36.3 per \AA)
integrated spectrum of a field in the bar of the Large Magellanic Cloud (LMC)
using EFOSC2 at the 3.6 meter telescope at La Silla Observatory. For this same
field, resolved stellar data reaching the oMSTO are available. We have compared
the star formation rate (SFR) as a function of time and the age-metallicity
relation (AMR) obtained from the integrated spectrum using {\tt STECKMAP}, and
the CMD using the IAC-star/MinnIAC/IAC-pop set of routines. For the sake of
completeness we also use and discuss other synthesis codes ({\tt STARLIGHT} and
{\tt ULySS}) to derive the SFR and AMR from the integrated LMC spectrum.
We find very good agreement (average differences 4.1 ) between the
SFR(t) and the AMR obtained using {\tt STECKMAP} on the integrated light
spectrum, and the CMD analysis. {\tt STECKMAP} minimizes the impact of the
age-metallicity degeneracy and has the advantage of preferring smooth solutions
to recover complex SFHs by means of a penalized . [abridged]Comment: 23 pages, 24 figures. Accepted for publication in A&A (6 Sep 2015
Observational Evidence of Accretion Disk-Caused Jet Precession in Galactic Nuclei
We show that the observational data of extragalactic radio sources tend to
support the theoretical relationship between the jet precession period and the
optical luminosity of the sources, as predicted by the model in which an
accretion disk causes the central black hole to precess.Comment: 13 pages, 1 figure, accepted for publication in ApJ Letter
The puzzle about the radial cut-off in galactic disks
The stellar disk in a spiral galaxy is believed to be truncated physically
because the disk surface brightness is observed to fall faster than that for an
exponential in the outer, faint regions. We review the literature associated
with this phenomenon and find that a number of recent observations contradict
the truncation picture. Hence we question the very existence of a physical
outer cut-off in stellar disks. We show, in this paper, that the observed drop
in the surface brightness profiles in fact corresponds to a negligible decrease
in intensity, and that this minor change at the faint end appears to be
exaggerated on a log-normal plot. Since minor deviations from a perfect
exponential are common throughout the disk, we suggest that such a deviation at
the faint end could easily give rise to the observed sharp drop.Comment: 4 pages, 3 .eps figures, Astron. & Astrophys Letters, In pres
Role of c-miR-21, c-miR-126, Redox Status, and Inflammatory Conditions as Potential Predictors of Vascular Damage in T2DM Patients
The development of type 2 diabetes mellitus (T2DM) vascular complications (VCs) is
associated with oxidative stress and chronic inflammation and can result in endothelial dysfunctions.
Circulating microRNAs play an important role in epigenetic regulation of the etiology of T2DM. We
studied 30 healthy volunteers, 26 T2DM patients with no complications, and 26 T2DM patients with
VCs, to look for new biomarkers indicating a risk of developing VCs in T2DM patients. Peripheral
blood samples were used to determine redox state, by measuring the endogenous antioxidant
defense system (superoxide dismutase, SOD; catalase, CAT; glutathione reductase, GRd; glutathione
peroxidase, GPx; and glucose-6-phosphate dehydrogenase, G6DP) and markers of oxidative damage
(advanced oxidation protein products, AOPP; lipid peroxidation, LPO). Additionally, inflammatory
marker levels (IL-1, IL-6, IL-18, and TNF- ), c-miR-21, and c-miR-126 expression were analyzed.
T2DM patients showed the highest oxidative damage with increased GSSG/GSH ratios, LPO, and
AOPP levels. In both diabetic groups, we found that diminished SOD activity was accompanied by
increased CAT and decreased GRd and G6PD activities. Diabetic patients presented with increased
relative expression of c-miR-21 and decreased relative expression of c-miR-126. Overall, c-miR-21,
SOD, CAT, and IL-6 had high predictive values for diabetes diagnoses. Finally, our data demonstrated
that IL-6 exhibited predictive value for VC development in the studied population. Moreover, c-miR-
21 and c-miR-126, along with GPx and AOPP levels, should be considered possible markers for VC
development in future studies.University of GranadaEugenio Rodriguez Pascual Foundation ERP-2021CIBERfes (ISCIII, Spain) CB16-10-0023
Detection of a Corrugated Velocity Pattern in the Spiral Galaxy NGC 5427
Here we report the detection, in Halpha emission, of a radial corrugation in
the velocity field of the spiral galaxy NGC 5427. The central velocity of the
Halpha line displays coherent, wavy-like variations in the vicinity of the
spiral arms. The spectra along three different arm segments show that the
maximum amplitude of the sinusoidal line variations are displaced some 500 pc
from the central part of the spiral arms. The peak blueshifted velocities
appear some 500 pc upstream the arm, whereas the peak redshifted velocities are
located some 500 pc downstream the arm. This kinematical behavior is similar to
the one expected in a galactic bore generated by the interaction of a spiral
density wave with a thick gaseous disk, as recently modeled by Martos & Cox
(1998).Comment: Accepted for publication in Ap
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